You think you're funny? Laugh it up. An age? Simple subtraction, right? Not quite...
Start with kids under an arbitrary cutoff limit (often customizable by HC org, department, and/or provider whose ages need to be given in months. Then you get bitching from neonatologists who want the age of kids under some other arbitrary limits to be displayed in days. This is for a relatively simple concept.
Now, multiply the whole thing by about 25,000 concepts (many more complex than "age"), riddle the whole thing with massive amounts of subjective judgement, toss in prima dona providers, constantly changing governmental regulations, constantly changing clinical standards, constantly changing knowledge and technology, and you can start to see how stupid your comment about age starts to look. It's a difficult domain to program for - try it sometime and see.